The output suddenly reaches maximum when DCS is turned on automatically.
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Our factory uses Foxboro's I/A system and has been using it for more than 4 years. Yesterday, suddenly the output of two loops suddenly mutated from about 40% to the maximum during automatic operation, and the given value also mutated to the maximum subsequently, causing great fluctuations in production. The configuration should be fine. An hour after the automatic operation was turned on again, the output mutation occurred again. After the output mutation, the given value also mutated to the maximum. I don't know the reason. Now it is running manually and no abnormality occurs. I would like to ask experts how to solve the problem. Thank you!
I suspect it has something to do with the primary measurement part of this control loop； Changes in process conditions are also not excluded. The reason is that your situation occurs automatically. After the output mutates, the given value also mutates to the maximum. It should be that the system thinks there is a problem based on the change rate, and the AUT is forced to the MAN state. A while ago, I had an incident where the steam pressure control valve automatically ran to the minimum. The reason was found to be that the craftsman operated the regulating valve across the line, causing the pressure measuring point behind the valve to be unable to adjust with the valve, and the regulating valve was fully closed in the automatic state.
I think we should take a closer look at whether the given value changes first or the output changes first. It may be the PV tracking function (PV tracking function is available in Yokogawa and Honeywell, I don’t know if it is available in Foxboro)
1. If the faulty detection circuit is the AI circuit, check whether there is external interference and whether the working grounding is complete. 2. Use the troubleshooting method to change the channel or replace the instrument.
Thank you for your answers. Foxboro technicians replied that it was a configuration problem. The specific reason was unclear. I deleted the previous PID module, changed the tag name, and made a new one. The fault was eliminated, but it reappeared a week later. This phenomenon also occurs when turning on the manual. I replaced the card and it has been running for a week and no similar phenomenon has occurred. I am observing it. Thank you! This post was last edited by best1976 on 2008-1-21 11:49 ]
Under normal circumstances, didn't this happen without changing the configuration? If so, the problem is too serious. If the configuration is changed, which part of the change causes this situation? It seems like this is what we should be working on! Otherwise, similar incidents will happen again. You can't just leave it at that if you can't explain the reason, right? Then check: lol